Production of hydrazine



Patented Apr. 13, 1954 PRODUCTION OF HYDRAZINE .iHerbert. J.;-Pas,sino, Englewood, N. J., assignor to "lT n .KelloggCompanY, Jersey City, N.J.,

ta. corporation of Delaware No Drawing. Application ctober23, 1950,

Serial No. 191,735

13. Claims. 1

;.inr ention relates to qthe cproduction of hydrazine. 1 n ionetaspect the: invention :relates tor-a metho. for;-.the;;conversion.ofiurea to hydrezinezThi-szaapplicationziis acontinuation-inpart :--,;of my rprior Wand co-pending application Serial, No. .-Z3'3 ,99.4, .ifiled March L11, 1947, now abandoned, relating "to the production of thydrazin hydrate.i hasqheretofore been, manna iactured by reacting hypochlorite isolution with ammonia, ;the;;.hypochlorite solution being prepared from sodiumihydroxide and chlorine. The reactan o yth epr pai'ation:of hydrazine hydrate bythis :method are, therefore, 1,:2 molecules of -.z8'.mm0ma,.;1;molecu1e of chlorine ;and.2 mo1ecules g of sodium hydroxide for each .-;molecule. of hydrazinehydrate produced. j It has been, found th-atuthis, method-heatherjd advantage that the r la vely exp n iv acta ts nam ly, s d um hydroxide and {col rs me, r n tut o ly int rmediates in the=;pr ocess: and are; represented in the resulting products ,as relatively ,sworthless sodium chlorider andmater. Aside from the material loss whichthese products represent, their presence in -;the reaction product .is *a positive disadvan a e; s n ei hey; mu b tim tely. s p rate from he-h dra ine hydra e produ p duced.

It is an? object. of rthis, invention to provide -;an improved method ;for the ;productionof hydrazine.

,Anotherrobject of the invention is to provide an .improved, method for the production i of hydrazine ,which ,requires no expensive reagents that arelargely,recovered any. form other: than hydraz ne-onhydr zine hydra A further object.,.of ,the inventionis to ,provide a prqcess ,for the production. of hydrazine in which the recovery of, .the product-constitutes a ,relatively simplei operation.

A still further object ofitheinvention is to providee process .Ionthe, production of hydrazine at a. unit cost substantiallylowerthan,theprior process, referred to, abore.

' Other obj ects, andadvanta es inherent in the invention willibecome .-.apparent ..1 'rom the folcarbonyl forming. ,metalsuch, as nickeL, iron, ,co

bait, ruthenium, molybdenum, chromium and tunete .Qf "th s carbony rior me metals,

nickelris preferred :tor-carrying. out :.;,the process crim nventionqwhenremploy neo relatively low.

2 temperature, as more fully hereinafter. described, while iron is preferred when carrying out:the process of the invention at relativelyhighertemperatures.

.The reaction is carried outby contacting urea under proper reaction conditions i with i the carbony1- -forming metal .which is present in :an amount eifective to convert a substantial proportion ofgthe urea present to hydrazinaandato form a-metal carbonyl. The carbonyl-forming metalis present in an, amount equivalentto at least 2 weight percent .of 15116 ureapresent in the reactionzone. Itis found thatatleast such quantity of the, carbonyl-forming metal.must;be used to vproduce readily .isolatable .amounts i-of hydrazine. However, it ,is preferred rthat the carbonyl forming. metal be present in aniamount of, at, least weight per cent oftheurea, present in the reaction zone, while. an amount of the metal equivalent to. at least .50zweightperucent or" the urea present in the reaction zone has been foundto be most efiectiveinacarryingnont the, hydrazine producing reaction.

Thev above reaction is preferably carried .out by contacting urea with the carbonyl-formingmetal at temperaturesbetween about Caandrtemperaturesjjust below the temperature of: decomposition of urea. The decomposition .-.of izurea takes-place between about 132,;C..,and,about 150C. It is withinthe scope of the invention to carryout the reaction at temperaturestat which decomposition of urea takes place, orgatotemperatures above the temperature oi:.dec0mposition of urea; however, from a standpointofeconomics, such temperatures are not preferred.

In accordance with one modification of -,the invention, the urea is contacted while in a, molten condition with the .;carbony1forming 1 metal, uc wa ck or i onn, r a c withithis modification, it is preferred to operatmabore 132 C. and justbelowthe temperature of. .substantial decomposition of the urea. The molten urea-is flowed through a; granular mass-of the nickel or iron at atn-iospheric pressure. *Theheat of reaction issupplied, primarily, by the molten urea, but additional.heatdssuppli-ed by indirectheat exchange, if necessary,=to maintain the catalyst massat the desired;temperature. Under these conditions, the hydrazine ,product is formed asa; gas and; passes ut of $12118 :reaction zone with. carbon monoxide. If nickelgis employed, very little nickel ,carbonyl is found inathe; reaction mixture. and the: hydrazine. productyis recoveredby cooling at about 0. to separate :it from the carbon i monoxide. 1f iron is employed, some carbonyls may be formed but these are readily decomposed to carbon monoxide and iron. Some iron penta-carbonyl may be formed which may react with hydrazine and other reactants present to form a complex which decomposes to semicarbazide and iron tetra-carbonyl. These compounds are readily separated from hydrazine at temperatures above 113 C. The formation of the semicarbazide represents a comsumption of, at most, one-fifth of the available urea. This cannot be considered as a loss, however, since semicarbazide is a valuable prodnot.

In the above described modification, the iron or nickel carbonyl-forming metal functions as a true catalyst in that no stable metal compounds are formed, the principal products being hydrazine and carbon monoxide. If any metalcarbonyl is formed, it is rapidly decomposed at the relatively high reaction temperature. Under these conditions, the formation of semicarbazide or hydrazine dicarbonamide is minimized. When employing iron as the carbonyl-forming metal, a relatively high temperature, as indicated above, is necessary to maintain this condition. Such temperatures are also effective for the use of nickel as the carbonyl-forming metal. It should be noted, however, that temperatures below the melting point of urea may be effectively employed with nickel. This condition may be maintained with nickel at temperatures between about 60 C. and about 70 C. or higher.

In accordance with another modification of the invention, the contact of urea with the carbonyl-forming metal is effected at temperatures below the melting point of urea and at which the metal carbonyl is relatively stable. Under these conditions, nickel is preferably employed as the carbonyl-forming metal and temperatures within the range of about 40 C. to about 60 C. are utilized. It is preferred to employ a substantial excess of the nickel. Contact may be effected by intimately mixing nickel powder with powdered urea. 1e nickel having been previously heated to a temperature sufficiently high to heat the urea to the desired temperature and supply the heat of reaction. Liquid hydrazine is formed by this operation, while nickel carbonyl is produced as a gaseous reaction product. The term hydrazine is employed throughout this specification for the sake of convenience, but is intended, unless otherwise indicated, to include not only anhydrous hydrazine itself, which is produced for the most part in accordance with the present process, but also hydrazine hydrate as well.

The above reaction may be represented, in

general, by the following equation in which nickel is employed as a representative carbonyl-forming metal:

The thus formed carbonyl is then decomposed to carbon monoxide and the metal, which may be represented by the following equation:

The procedure for the recovery of the hydrazine product will depend upon the reaction conditions employed. When the reaction zone is maintained at a temperature above the melting point of urea, gaseous hydrazine and carbon monoxide are the principal eflluents. Some semicarbazide and iron tetra-carbonyl may be formed, but these are readily separated by cooling th efiluents to temperatures at which the hydra- 4 zine remains in the vapor form. The mixture 01' hydrazine and carbon monoxide is then fractionated in a suitably packed fractionating tower to yield a hydrazine product essentially free from metal carbonyls.

In instances where the reaction temperature is below the melting point of urea but above the .boiling point of hydrazine, the principal gaseous effluent is gaseous hydrazine, although some carbon monoxid may be present and some iron carbonyl may remain with unconverted solid urea. The eflluent vapors are freed from iron carbonyl by beingheated to temperatures between about C. and about C.

When reaction temperatures below the boiling point of hydrazine are employed, the gaseous efiluent is essentially carbon monoxide. This gaseous efiiuent may also include metal carbonyl vapors, depending upon the particular metal employed and upon the reaction temperature. When nickel is employed at'a relatively low temperature, nickel carbonylvapors may be present in the eiiluent gas in greater quantity than carbon monoxide. The liquid hydrazine product and accompanying unreacted urea is removed from the reaction zone and maintained at a temperature between about 60 C. and about 80 C. for approximately 10 to 60 minutes to decompose nickel carbonyl. The product is then separated from any nickel which has settled out and is then distilled, preferably by flash distillation, to remove hydrazine as rapidly as possible from un-i reacted urea. Unreacted urea and recovered nickel catalyst may then be recycled to the operation. It will be understood that when the gaseous effiuent comprises largely nickel carbonyl, this material is separately heated to a temperature above the decomposition temperature of nickel carbonyl to recover nickel for reuse as a catalyst.

Preferably the reaction is carried out at low pressure, for example, atmospheric pressure or slightly higher pressure, as high pressure apparently causes the hydrazine product to react with urea with resulting loss of hydrazine.

Having thus described my invention, I claim:

1. A method for producing hydrazine which comprises: flowing molten urea through a granular mass comprising a carbonyl-forming metal-in a reaction zone, said carbonyl-forming metal being continuously maintained in an amount equivalent to at least 2 per cent by weight of the quantity of urea present in said reaction zone, at a temperature between about 132 C. and below the temperature of substantial decomposition of urea to convert at least a substantial quantity of urea present to hydrazine; and recovering hydrazine as a product of the process.

2. Th process of claim 1 in which the carbonyl forming metal is iron.

3. The process of claim 1 in which the carbonyl-forming metal is nickel.

4. The process of claim 1 in which the carbonyl-forming metal is cobalt.

5. The process of claim 1 in which the carbonyl-forming metal is molybdenum.

6. The process of claim 1 in which the carbonyl-forming metal is tungsten.

7. A method for producing hydrazine which comprises: flowing molten urea through a granular mass comprising a carbonyl-forming metal in a reaction zone, said carbonyl-forming metal being continuously maintained in an amount equivalent to at least 10 per cent by weight of the quantity of urea present in said reaction zone, at a temperature between'about 132 C. and below the temperature of substantial decomposition of urea to convert at least a substantial quantity of urea present to hydrazine; and recovering hydrazine as a product of the process.

8. A method for producing hydrazine which comprises: flowing molten urea through a granular mass comprising a carbonyl-forming metal in a reaction zone, said carbonyl-forming metal being continuously maintained in an amount equivalent to at least 50 per cent by weight of the quantity of urea present in said reaction zone, at a temperature between about 132 C. and below the temperature of substantial decomposition of urea toconvert at least a substantial quantity of urea present to hydrazine; and recovering hydrazine as a product of the process.

9. A method for producing hydrazine which comprises: flowing molten urea through a granular mass comprising a carbonyl-forming metal in a reaction zone, said carbonyl-forming metal being continuously maintained in an amount equivalent to at least 50 per cent by weight of the quantity of urea present in said reaction zone, at a temperature between about 132 C. and below the temperature of substantial decomposition of urea to convert at least a substantial quantity of urea present to hydrazine and produce a gaseous efiluent comprising hydrazine and carbon monoxide; withdrawing said efiluent from said reaction zone; cooling the effluent thus withdrawn; and recovering hydrazine from said cooled eifiuent.

10. A method for producing hydrazine which comprises: flowing molten urea through a granular mass comprising iron in a reaction zone, said iron being continuously maintained in an amount equivalent to at least 50 per cent by weight of the quantity of urea present in said reaction zone, at a temperature between about 132 C. and below the temperature of substantial decomposition of urea to convert at least a substantial quantity of urea present to hydrazine and produce a gaseous effluent comprising hydrazine and carbon monoxide; withdrawing said efiluent from said reaction zone; cooling the effluent thus withdrawn; and recovering hydrazine from said cooled efiluent.

11. A method for producing hydrazine which comprises: flowing molten urea through a granular mass comprising nickel in a reaction zone. said nickel being continuously maintained in an amount equivalent to at least 50 per cent by weight of the quantity of urea present in said reaction zone, at a temperature between about 132 C. and below the temperature of substantial 6 decomposition of urea to convert at least a substantial quantity of urea present to hydrazine and produce a gaseous efiluent comprising hydrazine and. carbon monoxide; withdrawing said efliuent from said reaction zone; cooling the efiluent thus withdrawn; and recovering hydrazine from said cooled effluent.

12. A method for producing hydrazine which comprises: flowing molten urea through a granular mass comprising a carbonyl-forming metal in a reaction zone, said carbonyl-forming metal being continuously maintained in an amount equivalent to at least 2 per cent by weight of the quantity of urea present in said reaction zone, at a temperature between about 132 C. and below the temperature oi substantial decomposition of urea to convert at least a substantial quantity of urea present to hydrazine and produce a gaseous efiluent comprising hydrazine and carbon monoxide; withdrawing said effluent from said reaction zone; cooling the efliuent thus withdrawn; and recovering hydrazine from said cooled effluent.

13. A method for producing hydrazine which comprises: flowing molten urea through a granular mass comprising a carbonyl-forming metal in a reaction zone, said carbonyl-forming metal action zone; cooling the efiiuent thus withdrawn;

and recovering hydrazine from said cooled efiluent.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 910,858 Raschig Jan. 26, 1909 2,129,689 Hetherington Sept. 13, 1938 2,527,315 MacKay Oct. 24, 1950 FOREIGN PATENTS Number Country Date 583,504 Great Britain Dec. 19, 1946 OTHER REFERENCES Chemistry of Hydrazine by Audrieth and ggxgr, pages 32-36, 1951 ed., John Wiley and Sons, 

1. A METHOD FOR PRODUCING HYDRAZINE WHICH COMPRISES: FLOWING MOLTEN UREA THROUGH A GRANULAR MASS COMPRISING A CARBONYL-FORMING METAL IN A REACTION ZONE, SAID CARBONYL-FORMING METAL BEING CONTINUOUSLY MAINTAINED IN AN AMOUNT EQUIVALENT TO AT LEAST 2 PER CENT BY WEIGHT OF THE QUANTITY OF UREA PRESENT IN SAID REACTION ZONE, AT A TEMPERATURE BETWEEN ABOUT 132* C. AND BELOW THE TEMPERATURE OF SUBSTANTIAL DECOMPOSITION UREA TO CONVERT AT LEAST A SUBSTANTIAL QUANTITY OF UREA PRESENT TO HYDRAZINE; AND RECOVERING HYDRAZINE AS A PRODUCT OF THE PROCESS. 